RU123978U1 - WEARABLE RADIATION MONITOR - Google Patents

Abstract

Wearable radiation monitor, including a gamma-sensitive plastic scintillation detector, optically coupled to a photoelectronic multiplier, an amplifier-driver of signals from a photoelectronic multiplier, a battery-based power subsystem, a radio communication channel with a central computer, a communication channel with a satellite navigation system and an intelligent control module and processing information with a liquid crystal indicator, characterized in that it further comprises a neutron detector based helium gas-discharge meters, hardware and software connected to the intelligent module through an additional amplifier-driver.

Description

The inventive utility model of a portable radiation monitor (NORM) relates to detector systems designed to search (detect, localize) nuclear materials and radioactive substances (NM and PB) by their gamma and (or) neutron radiation. NORM can be used autonomously or be an integral part of mobile radiation monitoring systems to expand the functionality of the latter, especially when searching for nuclear materials and explosives in hard-to-reach areas. The tasks of searching and detecting NM and radioactive substances arise in cases of radiation accidents, or in cases of loss or intentional (malicious) removal and disposal of nuclear materials and radioactive substances, or in other cases of illegal (unauthorized) handling of nuclear materials, radioactive waste and radioactive waste. NORM can also be used for radiation monitoring of the area.

Known dosimeters-radiometers suitable for searching for radioactive substances by gamma radiation, in which Geiger-Muller counters are used as detectors (for example, the Bullfighter MKS-15D dosimeter-radiometer, the Chibis dosimeter-radiometer, the technical characteristics of which given in the catalog of the company "Dose" [Catalog "Equipment for radiation monitoring", NLP "Dose", on the website of the company]). However, the sensitivity of such devices is 10 ² -10 ³ times lower than the minimum required for search radiometers. Therefore, the indicated class of radiation monitoring devices intended for individual dosimetry is not suitable for solving the problems of searching for nuclear materials and radioactive substances.

It is appropriate to emphasize that it is customary to quantify the sensitivity of search radiometers with the values of detection thresholds regulated in the Russian Federation by GOST R 51635-2000 “Monitors of radiation of nuclear materials”. In accordance with the mentioned GOST, the gamma-ray detection threshold equal to the minimum recorded activity Q _{min of the} ¹³⁷ Cs gamma source, even for the “coarsest” (least sensitive) wearable PM III category should be no more than Q _min = 600 kBq. Moreover, the specified threshold corresponds to a distance of 1 m at a source velocity of not more than 0.5 m / s and a probability of false alarms of 0.05 (see table 1 in Appendix 1).

Our estimates show that under these conditions, the detection thresholds of the aforementioned dosimeters-radiometers MKS-10D, MKS-15D and close to them are no less than Q _min = 50 MBq. The analysis shows that to solve the problems of searching for radioactive substances by gamma radiation in large areas, only radiometers or dosimeters that use highly efficient solid-state scintillators are suitable.

A known search dosimeter ISP-RM1703MO-1K [Catalog "Radiation Monitoring Equipment", NLP "Dose", on the catalog / website of the company], which contains a detector based on a Csl-Tl crystal with dimensions 10 × 10 × 40 mm ³ . The sensitivity of such a detector is approximately 20-50 times higher than that of a gas-discharge detector, but nevertheless insufficient to meet the requirements of GOST R 51635-2000. In addition, the ICP-RM1703MO-1K device measures only gamma radiation and is not suitable for simultaneously recording both gamma and neutron radiation.

Known search gamma radiometer DKS-96V with a scintillation detection unit based on a Nal (Tl) crystal ⌀63 × 63 mm [], which is used to detect radioactive contamination and radiation sources in scrap metal, in cargoes of automobile and marine transport. DKS-96 V is advertised as “having no analogues in the Russian Federation in terms of sensitivity to gamma radiation”. DKS-96V is really almost 200 times more sensitive than devices on Geiger counters. This detector is suitable for solving the problems of searching for radioactive substances by gamma radiation in large areas in accordance with GOST R 51635. However, the DKS-96V is not suitable for simultaneously detecting both gamma and neutron radiation.

Known scintillation neutron detector (US Pat. No. 3,338,368 USA), including a moderator made of polyethylene or polypropylene, scintillator ⁶ LiI: Eu and PMT. The scintillator has a density of 4.06 g / cm ³ , the scintillation efficiency is 0.2-0.3 relative to that for NaI: T1, and the luminescence wavelength is 460 nm. The known scintillation detector can be used as a wearable radiation monitor for detecting neutron radiation, however, it is not suitable for simultaneous detection of both neutron and gamma radiation.

Known scintillation detector of fast neutrons (US Pat. 3398278 USA), including a moderator of polyethylene, a ZnS: Ag scintillator and PMT. The known scintillation detector can be used as a portable radiation monitor for detecting neutron radiation, however, it is not suitable for simultaneous registration and monitoring of both neutron and gamma radiation.

Known scintillation detector for radiation monitoring of neutrons (Pat. 2143711 RF, IPC G01T 1/20, 3/00) based on plastic and ⁶ Li-silicate glass, sensitive to both fast and thermal neutrons. The known detector contains a scintillation block and an electronic signal processing unit. However, the known scintillation detector is not suitable for use as a portable radiation monitor for the simultaneous detection of neutron and gamma radiation.

Known universal portable radiometer spectrometer MKS-A03-1E [, Scientific and Practical Center “Aspect”, Dubna], designed for the search (detection, localization) of nuclear materials and radioactive substances. A scintillation detector based on a Nal T1 crystal разм34 × 47 mm in size and neutron counters based on tubes filled with ³ He are built into the MKS-A03-1E instrument. However, the sensitivity of the gamma detector in the indicated device is low: in accordance with GOST R 51635, according to the detection threshold, the MKS-A03-1E device should be assigned to PM III category. (For more details and with the aim of comparing with the analogues mentioned above, specific numbers of detection thresholds are given in Appendix 1, Table 1). In addition, in the indicated device of the ISS there are no hardware and software for communication with the satellite navigation system (SNA) for linking the recorded radiation levels to specific points of the surveyed area. It should be emphasized that for the search and detection of NM and RS in controlled areas, the presence in the modern search instrument of communication with the SNA is considered absolutely necessary.

Closest to the claimed is a wearable radiation monitor NORM [(a). A.S. Shein, A.Yu. Derstuganov, L.V. Viktorov, A.L. Krymov, G.A. Kuntsevich, B.V. Shulgin. Wearable radiation monitor. Abstracts at the International Meeting "Problems of Applied Spectrometry and Radiometry" (PPSR-2011). St. Petersburg M .: "STC Expert Center", 2011, p.8. (b) A.S. Shein, A.Yu.Derstuganov, L.V. Viktorov, A.L. Krymov, G.A. Kuntsevich, B.V. Shulgin / Wearable radiation monitor // Information sheet of the Physics and Technology Institute of the Physics and Technology Institute of the Physicotechnical Institute, UrFU No. 15 of 11.02.2012], designed to search for sources of gamma radiation in large areas in remote places.]

The well-known wearable radiation monitor NORM includes a scintillation plastic detector (polystyrene with the addition of POPOP) with dimensions of 25 × 13 × 3.5 cm ³ ; PMT; power subsystem based on the battery; amplifier driver; an intelligent control module with a liquid crystal indicator, a radio channel (433 MHz, 10 mW) for communication with a central computer; communication channel with satellite navigation system SNA; easel backpack for carrying. The intelligent control module is equipped with special software for managing measurement procedures and providing synchronous second-by-second recording of measurement results (gamma radiation detector count rates with the coordinates of the measurement point received from the SNA) both in the local non-volatile memory and in the control center database via radio channel or over the communication channel RS485. The NORM device is highly sensitive: the threshold for detecting gamma radiation from ¹³⁷ Cs is (for the conditions specified in Appendix 1) Q _min = 65 kBq, which corresponds to wearable RM of the first category according to GOST R 51635-2000. However, the well-known wearable radiation monitor NORM does not have a channel for detecting neutron radiation, therefore it is not suitable for simultaneous registration of both neutron and gamma radiation.

The task of developing a utility model is to create a portable radiation monitor suitable for simultaneous recording of both gamma and neutron radiation in an autonomous mode, that is, suitable for monitoring the radiation situation associated with mixed radiation fields.

The problem is solved due to the fact that a portable radiation monitor including a gamma-sensitive plastic scintillation detector, optically coupled to a photomultiplier tube (PMT), an amplifier-driver of signals from a gamma detector, an intelligent module with a liquid crystal integrated to control and process information an indicator, a power subsystem, a radio communication channel with a central computer and a communication channel with a satellite navigation system, an neutron detector based on elievyh discharge counters in hardware and software associated with integrated intelligent module through an additional driver amplifier. Moreover, a special high-voltage converter for supplying helium counters is additionally introduced into the power subsystem based on the battery, which contained a high-voltage converter for powering the PMT, and the intelligent control module is equipped with additional software for controlling the procedures for detecting neutron radiation and for processing the information received from gamma and neutron sensors.

The composition of the proposed wearable radiation monitor is presented in the block diagram (figure 1), where the following conventions are used:

1. - a plastic scintillation detector (polystyrene with the addition of POPOP);

2. - photomultiplier tube (PMT);

3. - amplifier-driver of signals from a gamma detector;

4. - neutron detector based on helium gas-discharge counters;

5. - amplifier-driver of signals from a neutron detector;

6. - intelligent control module;

7. - liquid crystal indicator;

8. - power subsystem;

9. - a high voltage converter for powering the PMT divider;

10. - a high voltage converter for supplying gas discharge neutron counters;

11. - battery;

12. - a radio channel with an antenna for communication with a central computer;

13. - A communication channel with the SNA satellite navigation system (contains a separate antenna).

Structurally, all of the listed units and blocks that are part of the NORM are located in a single lightweight duralumin case attached to an easel backpack, which is necessary for the convenience of carrying the device when moving around the surveyed area (in difficult terrain). Nodes of the device body provide its shock-vibration-strength.

An example of a practical implementation of the design of the proposed NORM is presented in the sketch drawing, figure 2, where the following conventions are used:

1. - a plastic scintillation detector with dimensions of, for example, 25 × 13 × 3.5 cm ³ optically coupled to a PMT;

2. - a neutron detector based on three or more helium gas-discharge counters;

3. - electronic components (amplifiers, high voltage converters, intelligent control module);

4. - liquid crystal indicator;

5. - easel backpack;

6. - rechargeable battery;

7. - the antenna of the radio communication channel with the central computer;

8. - The antenna of the satellite navigation system (SNA).

The neutron counters are located in the same plane and are fixed next to the plastic scintillation detector.

The device operates in two possible functional modes: a) the main mode is the registration of gamma radiation; b) additional modes - registration of neutron radiation or simultaneous registration of gamma and neutron radiation. In the case of detecting gamma radiation, the sensor element of the detector is a plastic scintillation sensor (polystyrene with the addition of POPOP, or another plastic such as toluene + p-terphenyl or xylene + p-terphenyl, []). A photomultiplier tube PMT is used as a photodetector for counting light flashes (scintillations) arising from gamma radiation. Next, the signal from the PMT is fed to the driver amplifier, the information from the output of which is processed using the built-in intelligent module. As an example, the size of the scintillation detector (25 × 13 × 3.5 cm ³ ), according to our estimates, is close to optimal in terms of balancing two conflicting characteristics: a) the necessary sensitivity (which requires an increase in the size of the detector); b) a sufficiently small mass of the device (which is necessary for easy carrying).

If neutron radiation is detected, the sensor element of the radiation monitor is a detector based on a set of three or more small helium ( ³ He isotope) neutron counters of the SNM-42 type (length 153 mm, diameter 18.5 mm and weight 25 g), or SNM -32 (length 323 mm, diameter 18.5 mm and weight 42 g). The neutron detector is equipped with a power converter with an output voltage of more than 1500 V. A helium counter effectively detects only thermal neutrons. For them, the capture cross section is more than 4000 bar. Neutron radiation associated with fissile materials (they are the subject of search and detection during radiation monitoring) has a wide range of energies with a maximum in the range of units of MeV, that is, fast neutrons dominate in the spectrum. Fast neutrons will not be detected by a helium counter unless they are slowed down to thermal energies (fractions of eV). The function of the moderator of neutrons to thermal energies in the proposed utility model is performed by a hydrogen-containing plastic scintillator block - a polystyrene block having a thickness of 3.5 cm, sufficient to slow down a significant part of fast neutrons to thermal energies. Information from the SNM-42 or SNM-32 counters of the neutron channel in the form of pulses is transmitted to the electronics blocks - the amplifier driver and then to the built-in intelligent module - and is processed using additional algorithms similar to those used in the gamma channel. The neutron channel software is similar to the gamma channel software and solves the problems of controlling measurement procedures, primary (express) processing of measurement results, and ensuring synchronous second-by-second recording of the results of measurements of neutron radiation levels and signals from the SNA via the radio channel or RS485 communication channel to the database. The used algorithms for processing signals from detectors are described in the patent of the authors of the described utility model NORM [Method for searching and detecting sources of ionizing radiation / L.V. Viktorov, K.V. Ivanovskikh, Yu.G. Lazarev, V.L. Petrov, A.S. .Shein, B.V. Shulgin // RF patent №2242024. B. I., 1071272004, No. 34]. The sensitivity of the SNM-42 or SNM-32 counters to neutrons according to the technical conditions of ODO 339.281 TU is 0.8, which ensures the registration of 80 percent of thermal neutrons falling into the sensitive volume of the counters.

The NORM wearable monitor has the following specifications.

- The energy range of the recorded gamma radiation of 0.05 ... 3.0 MeV.

- The minimum recorded activity of the ¹³⁷ Cs gamma source at a distance of 1 m with a source velocity of not more than 0.5 m / s and a probability of false alarms of not more than 0.05 is Q _min1 = 65 kBq.

- The threshold for detecting neutron radiation when using three SNM-32 helium counters and under the same conditions of detection (at a distance of 1 m from the source, the speed of the source is not more than 0.5 m / s, the probability of false alarms is not more than 0.05) is 1 5 · 10 ⁴ neutron / s,

- The mass of the elements of the gamma channel (together with the battery) is not more than 9 kg. The mass of elements associated with the neutron channel is not more than 1.2 kg. The total weight of the monitor does not exceed 10.3 kg.

- The communication range over the radio channel is 250 ÷ 400 m.

The indicated threshold for detecting neutron radiation corresponds to category III neutron radiation monitors in accordance with GOST R 51635. If necessary, increase the sensitivity (lower the detection threshold), the number of helium counters in the NORM can be increased to 5.

The proposed utility model of a portable radiation monitor provides a technical effect: a portable radiation monitor is suitable for simultaneous and separate registration of both neutron and gamma radiation in an autonomous mode; It is suitable for searching (detecting and localizing) nuclear materials and radioactive substances by gamma and neutron radiation and for radiation monitoring of the terrain in mixed radiation fields. The indicated technical effect is achieved due to three important factors: ensuring the high sensitivity of the proposed portable radiation monitor, introducing a neutron channel into the device, as well as the availability of hardware and software for communication with the SNA in the device for linking the recorded radiation levels to specific points of the surveyed area.

Claims (1)

Wearable radiation monitor, including a gamma-sensitive plastic scintillation detector, optically coupled to a photoelectronic multiplier, an amplifier-driver of signals from a photoelectronic multiplier, a battery-based power subsystem, a radio communication channel with a central computer, a communication channel with a satellite navigation system and an intelligent control module and processing information with a liquid crystal indicator, characterized in that it further comprises a neutron detector based helium gas-discharge meters, hardware and software connected to the intelligent module through an additional amplifier-driver.

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